sql - modeling database with 2 simillar table -


i have database has product_sell , product_buy tables, these 2 tables different in few fields , each 1 has owns comment table 

product_sell >---< product_sell_cmt product_buy >---< product_buy_cmt

now , want ask modelling approach better ?

  • design 4 tables showed above

  • design product_sell , product_buy separately common comment table

  • merge 2 product tables in 1 table unused columns in rows or using 1 1 relations

since, use product_sell , product_buy , comments lonely in cases , useful indexing , performance have 4 separated tables ?


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